This is an interesting question however should be answered by a neuropathologist together with a person specialised in neuroimaging ( new methods). Good luck Yvonne

I searching for it because tDCS stimulation effects depend of orintation of electric field to the neurones in the cortex.

Maybe some kind transcranail ultrasound may work.But i know nothing about this method.

I dont know exactly what are you looking for. What I know is that there are a new neuroimaging method that is in developed and maybe could be usefuel for your purpose. It is functional infrarred spectroscopic. I had wrote about the use of this technics in neuroscience. This could be a begin. http://www.intechopen.com/books/neuroimaging-methods/functional-near-infrared-spectroscopy-fnirs-brain-studies-and-others-clinical-uses

This is an excellent question, however I have not heard of any method for determining the gyrification of the cortex.

I agree with Umberto Leon-Dominguez. Indeed, for what I know the functional infrared spectroscopy could be only a beginning. The determination of the gyrification index is already quite difficult with the 3D MRI because of the relative limitations of the technique in determining the edges of the various cortex sulci and curvatures. It has to be born in mind that these limitations certainly increases with f-nirs.

i think of fNIRS to but for NIRS is tisue higly transpaternt and react only to oxygenatin. Today NIRS it cant be used for my purpose because its like EEG placemet. But maybe be bolible construsct somthing like line of sensors and move aroud the head.Still remain a questin how gyrificiation change the NIRS .Its amy shows taht resolution is to low or didi not reognize the change of tissue. Maybe is posible use different wave lenght to this purpose.

But all of this is only a ideas.

tDCS efect is depend of neuron polarization if you imagine gyrus like a hill with grass (neurons pointed to tehe surface ) and use current trought a hill from one side to another . In on side of hill will be stimulated the tips and in other the roots. The stimulation have oposite effect on each site of the gyri.because thet is be goog knouw the gyrification to minimalize this unvanted effect.

i agree with dr: Yvonne you may need to find someone who is specialized as a pathologist and i hope you a good luck

It sounds to me like the issue is one of contrast. To measure the depth of the gyrus, you need to be able to measure both the tip of the gyrus, and the trough of the sylcys and evaluate the distance between them. To do this you need to have the surface of the brain contrast with both the rest of the brain and the cranial fluid surrounding it. To do this, we could try to find a method of finding just the edge by looking for some aspect that is unique to the outer edge of the cortex, or, we could take inexact images and use some form of post processing to bring out the edges such as an edge detection done on the image itself. By adding false color to the edge, we could increase it's contrast to make it easier to measure the change in depth of the gyrus, (Assuming I am correct in my guess as to what the issue is.)

I agree with Alberto Zani. NIRS is in the beginning of its history. NIRS dont only measure oxy-Hb and deoxy-Hb. In those wavelength or optical window you can measure citocrome c-oxidase too for example. It is a protein that measure directly the neuron activity. What you want to measure, you have to adjust the wavelength to the absorption characteristics of the tissue. For example, if you want to measure water, you have to design a NIRS with a wavelength more than 900 nm. It´s no hard, it´s only imagine, money and time. Sorry for my english!

Also, you could combine NIRS and others technology as ultrasound.

Ditto as just above!

The gyrification index is igual to Length of complete contour divided by Length of outer contour. Reference: Anat Embryol (1988)179:173-179.